water overflow

[BOOSTEDN12]

Sup people

I have a problem with my n12 and its driving me up the wall as soon as I drive the car a bit hard robot to robot water pushes back into the water overflow bottle so bad that it actually comes out the cap.

now I have replaced the head gasket I have put another head on that has been skimmed and also pressure tested I have also replaced the radiator cap it’s a lot better now it doesn’t happen as fast as it use to but it still happens and surely this can’t be right

Any ideas what might be causing this?

[tassuperkart]

have the system pressure tested.
next, what is the water temp doing when it start pressurising?
Is the temp rising?
Id be looking at whether the thermostat is working correctly and that the radiator is clean and not clagged up with sludge.

next issue, which is usually not likely is that the water pump imnpeller has corroded away due to lack of maintenance and not pumping correctly.

L8r
Oracle